This program is for predoctoral training of biological science PhD students for research careers in Cellular and Molecular Biology. This interdisciplinary program involves students and 44 faculty members primarily from the Divisions of Biology & Biological Engineering and of Chemistry & Chemical Engineering but also from Divisions of Geology and Engineering. It is a continuation of a training program supported at Caltech for the past 35 years by NIH. Subjects of special emphasis within Cellular and Molecular Biology include genetics and genomics, regulation of gene expression, signal transduction, eukaryotic cell biology, systems biology, synthetic biological circuits, biopolymers, and protein and cell structure. Interaction between the Divisions is evidenced by students who, although earning their PhD in one Division, carry out their thesis research mentored by a faculty member of another Division; by joint courses; by a less-formal interaction including research collaboration, and by interdisciplinary graduate programs in Biochemistry & Molecular Biophysics and in BioEngineering. The major components of the training activities are: 1) each student's individual research program, guided by faculty members and carried out within a group of other students and postdoctoral fellows having related interests; 2) core graduate courses including courses in bioinformatics and writing; 3) preparation for candidacy examinations; 4) formal and informal seminars and group meetings; 5) a course in responsible conduct of research, and 6) a research seminar during which CMB students present their own research. Predoctoral trainees are admitted to graduate study in each option based on highly selective admissions criteria, especially high quantitative aptitude and strong motivation for research. Trainees will be selected from admitted students, and will be those who have a primary interest in research in Cellular and Molecular Biology. Trainees are expected to pursue research careers that require training in Cellular and Molecular Biology; the superb record of our past trainees supports this expectation. Facilities are located in a complex of adjacent buildings. Multi-user facilities include cell sorting, biological imaging including cryoelectron microscopy, NMR and mass spectrometry, monoclonal antibody production, high throughput DNA sequencing, animal care and production of transgenic mice.